As someone enjoying a very successful weight-loss program, I found
this interesting.
<http://www.sciencedaily.com/releases/2004/06/040630081825.htm>
Artificial Sweetener May Disrupt Body's Ability To Count Calories,
According To New Study
WEST LAFAYETTE, Ind. -- Choosing a diet soft drink over a regular,
sugar-packed beverage may not be the best way to fight obesity,
according to new research from Purdue University. But the researchers
said this doesn't mean you should grab a regularly sweetened soft
drink instead.
Professor Terry Davidson and associate professor Susan Swithers, both
in the Department of Psychological Sciences, found that artificial
sweeteners may disrupt the body's natural ability to "count" calories
based on foods' sweetness. This finding may explain why increasing
numbers of people in the United States lack the natural ability to
regulate food intake and body weight. The researchers also found that
thick liquids aren't as satisfying – calorie for calorie – as are more
solid foods.
Based on the research, Davidson and Swithers suggest paying more
attention to calories consumed and engaging in regular exercise to
battle the bulge.
The Purdue's researchers' study, "A Pavlovian Approach to the Problem
of Obesity," appears in the July issue of International Journal of
Obesity. Davidson and Swithers, members of the Ingestive Behavior
Research Center at Purdue, suggest that being able to automatically
match caloric intake with caloric need depends on the body's ability
to learn that the taste and feel of food by the mouth suggests the
appropriate caloric intake. Much as Pavlov's dogs learned that the
sound of a bell signaled food, people learn that both sweet tastes and
dense, viscous foods signal high calories. This learning process
begins very early in life and perhaps without conscious awareness,
according to the researchers.
"The body's natural ability to regulate food intake and body weight
may be weakened when this natural relationship is impaired by
artificial sweeteners," said Davidson, an expert in behavioral
neuroscience. "Without thinking about it, the body learns that it can
use food characteristics such as sweetness and viscosity to gauge its
caloric intake. The body may use this information to determine how
much food is required to meet its caloric needs."
Over the past 25 years, there has been a dramatic increase in the
consumption of artificially sweetened foods and low viscosity,
high-calorie beverages, said Swithers, a developmental
psychobiologist.
"Incidence of overweight and obesity has also increased markedly
during this period," she said. "Our hypothesis is that experience with
these foods interferes with the natural ability of the body to use
sweet taste and viscosity to gauge caloric content of foods and
beverages. When you substitute artificial sweetener for real sugar,
however, the body learns it can no longer use its sense of taste to
gauge calories. So, the body may be fooled into thinking a product
sweetened with sugar has no calories and, therefore, people overeat."
Swithers said that the loss of the body's ability to gauge caloric
intake contributes to increased food intake and weight gain,
especially when people do not count calories on their own. A similar
dynamic is at work with foods' texture and thickness.
"Historically, we knew that our body learns that if the food is thick,
such as whole milk, it tends to have more calories than compared to a
thinner liquid such as skim milk," Swithers said. "Now, our research
reinforces this and takes it one step further, showing that our bodies
translate this information about perceived calories into a gauge to
tell us when to stop eating."
The researchers based their hypothesis on Pavlovian theory. Ivan
Pavlov, known for his work in the early 20th century, is famous for
his experiment in training dogs to associate food with the ringing of
a bell. After being conditioned to the bell, the dogs salivated when
they heard it – even when they did not see or smell food. Davidson and
Swithers propose that rats learn a similar relationship between the
taste or texture of a food and the calories it contains and may use
this information to control food intake and body weight.
Davidson and Swithers' findings are based on two studies.
In the first study, two groups of rats were given two different
sweet-flavored liquids. In the first group, both liquids were
sweetened with natural high-calorie sweeteners so there was a
consistent relationship between sweet taste and calories. For the
second group, one of the flavored liquids was artificially sweetened
with non-caloric saccharin so that the relationship between sweet
taste and calories was inconsistent.
After 10 days of exposure to the flavors, the rats were allowed to eat
a small amount of a sweet, high-calorie chocolate flavored snack. The
researchers compared the two groups' ability to compensate for the
calories contained in the chocolate snack. The rats that had
experienced the inconsistent relationship between sweet taste and
calories were less able to compensate for the calories contained in
the snack and ate more than the rats that had experienced the
consistent relationship between sweetness and caloric intake.
"This suggests that experience with the inconsistent relationship
reduced the natural ability of the rats to use sweet taste to judge
the caloric content of the snack," Swithers said.
In the second study, two groups of rats were given a high-calorie
dietary supplement along with their regular food every day for 30
days. Although the supplements were identical in calories and
nutritive content, they differed in viscosity. For one group the
supplement had the consistency of thick chocolate pudding, whereas for
the other group, the supplement was similar to chocolate milk.
Davidson and Swithers found that over the course of the study, the
rats given the milk-like supplement gained significantly more weight
than the rats given the more viscous, pudding-like supplement.
"This finding indicates that rats are less able to estimate and
compensate for the calories contained in liquids than in semi-solid
foods," Davidson said. "If the body is less able to detect and
compensate for calories contained in liquids, then intake of
high-calorie beverages compared to semi-solid or solid foods could
increase the tendency to gain weight."
The number of Americans consuming sugar-free products increased from
less than 70 million in 1987 to more than 160 million in 2000. During
the same period, the consumption of regular soft drinks increased by
more than 15 gallons per capita annually.
"Increased consumption of artificial sweeteners and of high-calorie
beverages is not the sole cause of obesity, but it may be a
contributing factor," Swithers said. "It could become more of a factor
as more people turn to artificial sweeteners as a means of weight
control and, at the same time, others consume more high-calorie
beverages to satisfy their cravings."
Davidson and Swithers are evaluating potential mechanisms that may
produce the short- and long-term effects on food intake and body
weight, as well as whether age or gender are contributing factors.
Additional research also will need to evaluate if the body and brain
can be retrained to naturally measure calories after consuming
artificial sweeteners or high-calorie beverages.
The National Institute of Child Health and Development, National
Institute of Digestive Diseases and Kidney Disorders, and Purdue
School of Liberal Arts funded this research.